There must be a massive market for small tracking devices not only for instruments, but for children and valuable objects of all sorts. A tiny tracker that could be switched on by the owner in the event of something ,or someone getting lost or stolen.Perhaps as suggested linked to mobile phones. Some of our instruments are worth thousands and with classical instruments over a million.Alternatively micro chipping that could easily be checked by Pawn shops, Auction Rooms Music Shops etc to make sure the instrument ,or object has not been stolen.
How lovely to knock on a thief's door and demand your favourite guitar or concertina back.
We can laugh about it, but even Nursing Homes and Old Folks homes have a problem of patients going off for a wander,
Al